Extended Data Fig. 3: Imaging speed comparison between broadband FTIR and single-frequency SRS.
From: Mid-infrared metabolic imaging with vibrational probes
a, Broadband FTIR microscope acquires a hyperspectral data cubic in a single scan. C-D image was generated as the transmittance difference between on-resonant (2140 cm-1) and off-resonant (2000 cm-1) with 3.3-μm pixel size. Noise was estimated as the spectral noise in the spectral region of 2100-2200 cm-1. 128 co-scans background was utilized. With 8 co-scans of signal measurement, total acquisition time is 80 min for 3.3-μm pixel size (25× objective), 30 min for 5.5-μm pixel size (15× objective) and 3 min for 20.2−μm pixel size (4× objective). b, Narrowband picosecond excitation was utilized in SRS microscope. C-D image was generated as the intensity difference between on-resonant (2135 cm-1) and off-resonant (2370 cm-1). 100-mW pump and 150-mW Stokes were utilized with 20-μs pixel dwell time and 20-μs lock-in time constant. Noise was estimated by the s.d. among pixels with only pump laser under the same laser power and lock-in time constant. Total acquisition time for a single frequency is about 20 min for 2-μm pixel size, and 80 min for 1-μm pixel size, respectively. Experiments in a and b were not repeated. Scale bars, 1 mm.
